LED night lighting improving mini-budding technology in Hevea brasiliensis

International Journal of Environment, Agriculture and Biotechnology Vol-6, Issue-1; Jan-Feb, 2021

Journal Home Page Available: https://ijeab.com/ Journal DOI: 10.22161/ijeab

LED night lighting improving mini-budding technology in Hevea brasiliensis Xing-Cheng Yao, Han-Qi Tu, Xin-Long Wang, Jun Wang*

Rubber Research Institute, Key Laboratory of Biology and Genetic Resources of Rubber Tree, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101，Hainan, China *Corresponding author

Received: 27 Nov 2020; Received in revised form: 12 Jan 2021; Accepted: 21 Jan 2021; Available online: 01 Feb 2021 ©2021 The Author(s). Published by Infogain Publication. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/).

Abstract— Mini-budding, exploiting seedlings of about 20 days, is a major technology for planting material propagation of rubber tree in China. The first pair leaves should be kept on rootstocks for assimilation. Manually axillary bud picking is needed to promote scion bud germination, but it is difficult and labor intensive. In this study, topping was carried out on the position below the first pair leaves and the subsequent plants were subjected to LED night lighting. The plant growth and the plant survival rate were improved by night lighting. The scion growth of the 1st flush was not comparable to that of plants with leaves on rootstocks. The high amount of chlorophyll content in the leaf might be response for this. The plant survival rate of the treatment was similar with that of plants with leaves on rootstocks. Thus, applying LED night lighting to the plants without leaves on rootstocks improved mini-budding technology by avoiding axillary bud picking.

Keywords— grafting, nursery, photoperiod, vegetative propagation, rubber tree.

I.

INTRODUCTION

(Dong et al., 1986).Therefore, the early growth of grafted

The Para rubber tree (Hevea brasiliensis Willd. Ex. A. de.

shoot is mainly controlled by the rootstock. In general, the

Juss.Müll-Arg.) is preferred over alternative sources of

larger size of rootstock, the more carbohydrate stored in

natural rubber worldwide due to the quality and quantity

the rootstock, and the stronger of germinating shoot.

of latex produced. The planting materials of rubber trees

There are several types of bud grafting according to

are vegetatively propagated by bud grafting (budding is

the

the colloquial term). The combined plants include clonal

Mini-budding(Figure 1), developed in the 1980s in China

scions and hetero-rootstocks. After grafted, the rootstock

by Huang (Huang, 1989), is carried out when the seedling

can affect the initiated growth of scion. The carbohydrate

rootstocks are as young as 2-3 weeks old. The diameter

for germination of grafted bud (scion) is directly provided

and height of seedling rootstock (graft position) is less

by the rootstock. The leaves of germinating shoots could

than 5 mm and 30 cm, respectively. One month after

not assimilate until at the stage of mid light green period

grafting, topping is carried out on the position just above

ISSN: 2456-1878 https://dx.doi.org/10.22161/ijeab.61.18

size

of

rootstocks

(Priyadashan,

2017).

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Xing-Cheng Yao et al.

International Journal of Environment, Agriculture and Biotechnology, 6(1)-2021

the first pair leaves. The axillary buds above the grafted

and could not supply sufficient carbohydrate for the shoot

bud are removed to eliminate apical dominance. Using

(scion) grow, at least one or two leaves must be kept on the

mini-budding, planting materials could be produced as

grafted root stocks for assimilation (Figure 1-C). However,

fast as 6 months after sowing seeds in the seedbed during

manually axillary budpicking is difficult and labor

August–September. Mini-budding is preferred in China

intensive. Axillary bud picking is practiced twice or thrice

because it reduces cost of production by decreasing the

sometimesbefore axillary buds are totally picked.

time and nursery area for production of grafted planting

Therefore, it is necessary to improve topping and

materials.

subsequent axillary bud picking for mini-budding plants.

As the rootstocks for mini-budding are quite small

Fig. 1: Mini-budding profile. (A),Seedlings suitable for mini-budding. Arrow: graft position. (B),Graft finished. (C), Scion shoot germination. Arrow: axially buds have been picked. (D), Grafting in a room.

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International Journal of Environment, Agriculture and Biotechnology, 6(1)-2021

Light is a key environmental factor regulating plant growth

by

affecting

photosynthesis.

Plant growth measurements

Extended

The plant height and stem (scion) diameter were

photoperiod can improve plant growth by synthesizing

monitored in May, July, September and November, 2020.

more carbohydrate. Supplemental lighting during the

The flush number and flush length were measured when

night extends the photoperiod and thus promotes plant

the experiment was finished in November, 2020. The stem

growth. Light-emitting diode (LED) lamps are the

diameter was measured at 5 cm above the shoot

preferred source for supplemental lighting due to their low

germinating position. The percentage of plant survival

operating temperature, durability and low cost (Singh et

(scion shoots that successfully grew to the stationary

al., 2015). Supplemental night lighting has been widely

phase of second flush) was calculated.

used in the production of crops and other plants to promote growth (Fukuda et al. 2000, 2004; Okushima et

Chlorophyll content analysis

al., 2012; Zhou et al., 2013; Kweon et al., 2016; Tewolde

After cutting off, the green bark of the rootstock stems

et al., 2016).

was analyzed for chlorophyll content. The green bark was

In this study, the min-budding rootstock plants were cut off on the position just below the first pair leaves (the first flush) when the plants grew to the stationary phase of the second flush. The grafted plants were then subjected to overnight LED lighting. The effect of LED night lighting on the growth of mini-budding plants was investigated.

peeled from the stems and the fresh weight of bark was measured. Approximately 0.1 g of bark tissue was ground and incubated in 20 ml of a mixture of acetone, ethanol and deionized water (4.5:4.5:1) in the dark for 24 h at 25°C. The absorptions of chlorophyll a andchlorophyll b were measured at 647 and 664 nm, respectively, using a spectrophotometer (TU-1810s, PERSEE, China). The chlorophyll content was calculated according to the

II.

MATERIALS AND METHODS

methods

of

Wellburn(1994).The

total

amount

of

chlorophyll of green bark was calculated as chlorophyll

Plant materials Hevea seeds of clone GT1 were sowed in August, 2019.

Mini-budding was carried out with scion clone CATAS 7-33-97 in September. The grafted plants were planted in polybags which were placed in an arched shed with sun shade cloth. Topping was carried out in November, 2019, when the grafted rootstock plants grew to the second

content multiplying fresh weight.The chlorophyll content of the first pair leaves kept on the rootstock was also analyzed. The fresh weight of the two trifoliate leaves (without petioles) was measured. The total amount of chlorophyll of leaf was calculated as chlorophyll content multiplying fresh weight.

Statistics analysis

flush.

The grafted plants were cut off on the position just

The statistical analyses were performed using SPSS 22.0

below the first pair leaves. Two treatments were carried

software. Significance at the 0.05 level was determined

out and each replicated thrice. Treatment one (designated

using Tukey’s multiple range test.

as Ⅰ-LED) was subjected to LED lamp night lighting.

LEDs were hung 0.5 m above the plants. The lamp spectrum

was

red

and

blue

combined

with

a

photosynthetic photon flux density (PPFD) of 200 μmol m-2 s-1 measured at 10 cm from the LED lamp.

Supplemental lighting was applied during the night from 19:00 to 06:00.Treatment two (designated as Ⅱ – no LED) was subjected to no LED night lighting. The plants obtained by conventional mini-budding were used as a control.

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III.

RESULTS AND DISCUSSION

The diameter of seedling rootstocks was measured when mini-budding was carried out. The mean diameter was 3.51 mm at the position of 3 cm above the root collar.

After cutting off on the position below the first pair leaves, the grafted plants were grown under the condition with or without supplemental LED night lighting. The plant height and stem diameter were monitored after growing 6, 8, 10 and 12 months. The plants of Ⅰ- LED exhibited larger

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International Journal of Environment, Agriculture and Biotechnology, 6(1)-2021

stem diameter and higher plant height than Ⅱ- no LED

length (figure 4). The 1st flush length of control plants

(Figure 2, 3), showing that supplemental LED night

(obtained from conventional mini-budding)was 14.35 cm,

lighting promoted plant growth.The plants of Ⅰ- LED grew

significantly longer than that of Ⅰ- LED (6.67 cm) and Ⅱ-

more flushes (mean 5.5) than that of Ⅱ- no LED (mean

no LED (5.43 cm). The stem diameter of control plants

4.6), which indicated that the rhythmic growth has been

was also larger than that of Ⅰ- LED when the shoots

accelerated. The mean flush length of plants of Ⅰ- LED

finished the first flush growth.This indicated that more

was significantly longer than that of Ⅱ- no LED (Figure 4).

carbohydrate has been assimilated by plants with leaves

The 1st,2nd, 3rd, 4th and 5th flush length between Ⅰ- LED

kept on rootstocks. Even though the grafted plants without

and Ⅱ- no LED were compared, respectively. The 3rd

leaves grew under night lighting, the carbohydrate they

flush length of Ⅰ- LED was significantly longer than that

assimilated was not comparable to that assimilated by the

of Ⅱ- no LED, but the other flushes showed similar flush

leaves in control plants.

Fig. 2: Comparison of stem diameter between Ⅰ– LED and Ⅱ– no LED.

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International Journal of Environment, Agriculture and Biotechnology, 6(1)-2021

Fig. 3: Comparison of plant height between Ⅰ– LED and Ⅱ– no LED.

Fig. 4: Comparison of flush length (FL) between Ⅰ– LED and Ⅱ– no LED.The earliest germinated flush was designated as the first flush.

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International Journal of Environment, Agriculture and Biotechnology, 6(1)-2021

The plant survival rate is an important index for

greatly.

evaluating seedling cultivation technology because it affects the production cost. The plant survival rate of Ⅰ-

IV.

LED and Ⅱ- no LED was92.3% and 45.4%, respectively.

CONCLUSION

There was significant difference between Ⅰ- LED and Ⅱ-

Mini-budding is a prevalent technology for vegetative

no LED. This implied that the plants of Ⅰ- LED could

propagation of rubber tree in China. The first pair leaves

assimilate during night lighting. Therefore, more

should be kept on rootstocks for assimilation when

carbohydrate had been synthesized, which was then

topping is conducted, but the axillary bud picking which is

utilized for shoot growth. The percentage of plant survival

labor intensive must be carried out. Mini-budding plants

of Ⅰ- LED (92.3%) was comparable with that of control

without leaves on the rootstock exhibited extremely poor

plants (93.4%).This indicated thatthe mini-budding plants

growth and low plant survival rate. LED night lighting

without leaves on rootstock could provide proper

could improve the growth as well as plant survival rate of

carbohydrate for normal shoot growth when grew under

mini-budding plants without leaves on the rootstock.

supplemental LED night lighting.

Therefore,

The chlorophyll content in the green bark tissue of young rootstock was 1.77 mg g-1 FW (fresh weight), which

suggested

that

the

green

bark

could

applying

LED

night

lighting

to

the

mini-budding plants without leaves on the rootstock improved mini-budding technology by avoiding axillary bud picking.

photosynthesize. The chlorophyll content in the leaves was much higher (3.62 mg g-1 FW). The fresh weight of

ACKNOWLEDGEMENT

leaf was 3 times of that of green bark. The total

The study was financially supported by China Agriculture

chlorophyll amount in the bark tissue and the leaves was

Research System (CARS-33-YZ4).

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